import math
x1,y1,x2,y2=map(float,input().split())
print(f'{math.sqrt((x2-x1)**2+(y2-y1)**2):.5f}') import math math x1,y1,x2,y2=map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 print(f'{math.sqrt((x2-x1)**2+(y2-y1)**2):.5f}') print f'{math.sqrt((x2-x1)**2+(y2-y1)**2):.5f}' y2=map(float,input().split()) map(float,input().split()) y2 x2,y2=map(float,input().split()) map(float,input().split()) x2 x1,y1,x2,y2=map(float,input().split()) map(float,input().split()) x1 y1,x2,y2=map(float,input().split()) map(float,input().split()) y1
import math
x1,y1,x2,y2=map(float,input().split())
print(f'{math.sqrt((x2-x1)**2+(y2-y1)**2):.5f}')
